What Fraction of Global Warming is Due to the Radiative Forcing of Increased Atmospheric Concentrations of CO2?

This is a long weblog. The bottom line conclusions are written here to motivate reading the entire weblog.

CONCLUSIONS:

1. The primary focus on carbon dioxide inappropriately deemphasizes the first order importance of the other climate system heat system forcings (both cooling and warming forcings), as well as does not address the spatially complex, and incompletely understood, actual pattern of global climate system heat changes.

2. Attempts to significantly influence regional and local-scale climate based on controlling CO2 emissions alone is an inadequate policy for this purpose.

A starting point for the assessment of the relative fraction of global warming that is attributable to the radiative forcing of CO2 is the Summary Figure from the 2002 IPCC report (see). Clearly, according to their analysis, in comparing the change of radiative forcing since pre-industrial times until the present as estimated from the IPCC summary figure, the well-mixed greenhouse gases dominate the forcings which cause warming (about a 2.4 Watts per meter squared difference between these two time periods), of which about 1.4 Watts per meter squared is from CO2. Other warming forcings that they include, if the mean value plotted is used, are black carbon from burning fossil fuels (about 0.2 Watts per meter squared), tropospheric ozone (about 0.3 Watts per meter squared), and solar (about 0.25 Watts per meter squared).

Using these values about 58% of the radiative forcing of the well-mixed greenhouse gases results from CO2, and about 48% of the warming human-caused climate forcings result from the radiative forcing of CO2.

The following extracts from research studies reduce the relative contribution of the radiative forcing of CO2 as reported in the 2002 IPCC Report, as summarized above. These studies report the following,

“NASA scientists have found that a major form of global air pollution involved in summertime “smogâ€? has also played a significant role in warming the Arctic……According to this new research, ozone was responsible for one-third to half of the observed warming trend in the Arctic during winter and spring. Ozone is transported from the industrialized countries in the Northern Hemisphere to the Arctic quite efficiently during these seasons. â€?
(see).

â€?Even within the well-mixed greenhouse gas forcings, there are new complications. Drew Shindell and colleagues, as reported in Pollution Online found that, ’According to new calculations, the impacts of methane on climate warming may be double the standard amount attributed to the gas. The new interpretations reveal methane emissions may account for a third of the climate warming from well-mixed greenhouse gases between the 1750s and today. The IPCC report, which calculates methane’s affects once it exists in the atmosphere, states that methane increases in our atmosphere account for only about one sixth of the total effect of well-mixed greenhouse gases on warming. ’â€? (see).

Moreover, from the 2006 Nature paper “Methane emissions from terrestrial plants under aerobic conditions” by Keppler et al,

” If our measurements are typical for short-lived biomass and scaled on a global basis, we estimate a methane source strength of 62–236 Tg yr-1 for living plants and 1–7 Tg yr-1 for plant litter (1 Tg = 1012 g). We suggest that this newly identified source may have important implications for the global methane budget and may call for a reconsideration of the role of natural methane sources in past climate change.”

“A recent study by the CERES Science Team has added to the uncertainty associated with the contributions of climate forcings to global warming by finding that for the period 2000-2004, their assessment of the shortwave albedo decreased by 0.0015 which corresponds to an extra 0.5 Watts per meter squared of radiative imbalance according to their assessment. (see)

“Deposition of BC aerosols over snow-covered areas can result in changes to the surface albedo (Chylek et al. 1983). Further reductions in albedo occur due to the enhanced melting that accompanies the heating of absorbing soot particles in snow. Chylek et al. (1983) estimate this enhancement to be up to a factor of ten in the rate of melting. Recent model results indicate radiative forcings of +0.3 W m−2 in the Northern Hemisphere associated with albedo effects of soot on snow and ice (Hansen and Nazarenko 2004).â€? (see)

We can summarize these findings below:

i) “ozone was responsible for one-third to half of the observed warming trend in the Arctic during winter and spring”.

ii) “The new interpretations reveal methane emissions may account for a third of the climate warming from well-mixed greenhouse gases between the 1750s and today”.

iii) “for the period 2000-2004, their assessment of the shortwave albedo decreased by 0.0015 which corresponds to an extra 0.5 Watts per meter squared of radiative imbalance according to their assessment.”

iv) “Recent model results indicate radiative forcings of +0.3 W m−2 in the Northern Hemisphere associated with albedo effects of soot on snow and ice”

v) There are a variety of direct and indirect aerosol effects that cause global warming including the black carbon direct effect, the semidirect indirect effect, and the glaciation indirect effect, with the thermodynamic effect having an unknown influence (see).

If we use the IPCC estimate of the fraction of the radiative forcing change of the well-mixed greenhouse gases from the pre-industrial to the present (i.e. see), which is about 2.4 Watts per meter squared, we can use the estimates of the radiative forcing from the other human climate forcings that are listed above to compare with this value, and with the fraction of the well-mixed greenhouse gas forcing that is due to CO2.

It need to be emphasized that the IPCC figure of the radiative forcing of 1.4 Watts per meter squared due to CO2 is not the current radiative imbalance since, presumably, some of the imbalance earlier in the industrial period with respect to CO2 increases has been removed as the climate system warmed. Nonetheless, these values can be used to scale the relative contribution to global warming due to the radiative effect of CO2. Also, since the observed radiative imbalance based on the 2004 Willis et al assessment is significantly less than the change from preindustrial to the present, the effect of human climate forcings that cool the climate system are, of course, also occurring.

With respect to the finding listed above, methane has a value of 0.8 Watts per meter squared, the shortwave albedo change is 0.5 Watts per meter squared, and the albedo effect of soot is 0.3 Watts per meter squared (which, however, may not be independent of the “shortwave albedo change). Tropospheric ozone, the aerosol black carbon direct effect, the semidirect indirect effect, and the glaciation indirect effect also add Watts per meter squared.

By summing the 0.8 Watts per meter squared for methane and using the total of 2.4 Watts per meter squared of the well-mixed greenhouse gases from the IPCC Report, the radiative contribution of CO2 reduces to about 46% of this component of radiative forcing (1.1 Watts per meter squared). The 46% value, of course, assumes that none of the radiative forcing of CO2 emitted earlier in the industrial period has equilibrated, so that the 46% is actually a high number, but is used here to be conservative.

For all of the human-caused warming radiative forcings, which includes the 0.5 Watts per meter squared value for the shortwave albedo change, and estimating tropospheric ozone as 0.3 Watts per meter squared, the aerosol black carbon direct effect as 0.2 Watts per meter squared, the black carbon on snow and ice as 0.3 Watts per meter squared, the semidirect indirect effect as 0.1 Watt per meter squared, and the glaciation indirect effect as 0.1 Watt per meter squared (with the latter two forcings using a nominal value, since these forcings are very poorly known), the contribution due to CO2 will fall to about 28%.

This analysis also ignores solar influences on the heating in which a published paper concludes,

“We estimate that the sun contributed as much as 45–50% of the 1900–2000 global warming, and 25–35% of the 1980–2000 global warming. ‘ (see). Even the IPCC estimates that there has been a warming influence from the Sun in their radiative forcing summary figure of about 0.25 Watts per meter squared (see). Adding this 0.25 Watts per meter squared value reduces the percent contribution of CO2 to about 26.5%.

This calculation does not mean that there is not merit in reducing the human input of CO2 into the atmosphere, but it does mean that even in the context of global warming, it is only a fraction of the actual positive radiative forcings.

This specific weblog focuses on the specific subset of climate variability and change that is referred to as “global warming” However, the assessment of radiative forcing directly is not the most appropriate procedure to use to assess global climate system heat changes. As was discussed in 2003 in “Heat storage within the Earth system”, the ocean heat content change is the proper metric to monitor.

Moreover, the observed ocean heat content changes have been spatially complex as has been discussed on this weblog (see and see). As reported based on the paper in 2004 by Willis et al that has been discussed on Climate Science (e.g. see and see),

“Maps of yearly heat content anomaly show patterns of warming commensurate with ENSO variability in the tropics, but also show that a large part of the trend in global, oceanic heat content is caused by regional warming at midlatitudes in the Southern Hemisphere.â€?

This heating is

“…centered on 40S is spread more uniformly over the water column and warms steadily throughout the entire time series…â€?

The climate science that is presented in this weblog summarizes one of the reasons for the conclusion that,

‘Attempts to significantly influence regional and local-scale climate based on controlling CO2 emissions alone is an inadequate policy for this purpose. ” (see).

The primary focus on carbon dioxide inappropriately deemphasizes the first order importance of the other climate system heat system forcings (both cooling and warming forcings), as well as does not address the spatially complex, and incompletely understood actual pattern of global climate system heat changes.

Review of A Book on Land Use Change Effects

In 2004 I completed a review of a book which is very relevant to the discussion of land use change as a climate forcing and on the vulnerability perspective that has been emphasized on the Climate Science weblog. This review is reproduced below with respect to this book.

Pielke, R.A. Sr., 2004: Book Review of Global environmental change and land use by H. Dolman et al. Bull. Amer. Meteor. Soc., July, 1005-1006.

This book, completed in early 2002 and published in 2003, focuses on the contributions of the Netherlands National Research Programme on the topic of global environmental change as influenced by land-use change, and places their work in a global context. This group has been a leader in this research area; therefore, this book is an internationally valuable reference source.

The text is segmented into eight chapters that are written by one or more authors. Chapter 1 gives an overview of the topics of land use and global environmental change. Among its important summaries is the large fraction of the Earth’s land surface that has been altered by human activities. Concurrent with land surface changes have been human disturbances to the global geochemical cycles, including the well-mixed greenhouse gases (CO2, CH2, N2O), but also a variety of other chemical species and effects, such as nitrogen deposition. Chapters 2 and 3 discuss the multidimensional character of land-use change, including micro- and macro-level analyses. The modeling of land-use change is discussed, including economic and other forcings of land-use change. This chapter is particularly valuable for atmospheric scientists, hydrologists, and ecologists who want to learn more about the important role of land-use change on the climate system.

Chapter 3 also discusses policies to mitigate climate change through land use. One issue I have with this section is the lack of discussion of how the mitigation process itself can feed back to alter the water and energy budget of the atmosphere, as discussed in chapter 4. Chapter 4 introduces the very important concept that the Earth’s land cover and vegetation interact within the climate system across diverse space and time scales. This topic is very well overviewed in this
chapter, including a discussion of land-use change effects in the Amazon and in the Sahel region of Africa.

One disagreement I have is their conclusion of “weak coupling” with biogeochemical and soil chemical processes, which they state is important on “very long time scales: one to several hundreds of years.” As shown by Lu et al. (2001), for example, using a coupled atmosphere-ecological modeling system, these feedbacks can occur on monthly and shorter time scales, at least in grasslands. Chapter 5 focuses on terrestrial carbon sources. Since the researchers who coauthor this chapter are world-recognized leaders on this subject, the text is a very informative current summary of the global carbon budget as influenced by land-surface processes.

Chapter 6 extends the discussion of budgets to the hydrologic cycle, including the effect of land-surface changes, such as deforestation and reforestation. One comment is that the authors separate the terms “climate” and “hydrology,” when-as they clearly demonstrate in chapter 4- hydrological processes are an integral component of climate. A study of the role of land in West Africa, with a focus on food security, is provided in chapter 7. Unfortunately, part of the chapter relies too heavily on general circulation model results as predictions (out to 2050), rather than a more comprehensive assessment of vulnerability of West Africa to the entire spectrum of climate risks to food. Nonetheless, if one interprets these results as sensitivity analyses, the chapter provides important insight into the climate risks that face the food supply in this region. The general topic of food security in this chapter is very informative and will help educate the reader on the complexity of this topic. The final chapter discusses the use of renewable energy sources. This section provides an interesting summary of energy supply on a global scale and for the Netherlands.

An Earlier Paper on the Role of Regional Land Surface Change and Regional Aerosol Emissions As First-Order Climate Forcings

Professor Dev Niyogi has alerted me to another important paper that was published in a journal that is normally not read by climate scientists. This paper, published in 1994, provides important background information on why land surface processes are so important as climate forcings.

The paper is the “Effects of pre-industrial human activities on climate” (subscription required) which appeared in Chemosphere and was written by Alan Robock and Hans-Friedrich Graf in 1994. The abstract states,

“Pre-industrial human activities which changed the atmospheric greenhouse gas or aerosol loading, or which modified the properties of the earth’s surface, such as albedo, roughness, or vegetation cover, had the potential to modify the regional or even global climate. The primary activities which could have produced these effects were deforestation, burning, and agriculture. These activities were not independent, and often occurred together. Deforestation could have produced warming or cooling at the surface, and different effects on different scales, depending on the fate of the biomass removed and the new use of the land. Burning is much less now than it was in the past in some regions, which would have produced warming as the burning decreased. This may be a partial explanation for the Little Ice Age. While a thorough survey of such pre-industrial human activities is called for, current information indicates that regional climatic effects were large in some regions, such as western North America, and hemispheric or global effects were possible. Once these pre-industrial human climatic forcing factors are better quantified, existing numerical models of the climate can be used to examine the impacts on regional and global scales. ”

The text includes the statements,

“Anthropogenic activities can affect climate in a number of well-known ways (Houghton et al., 1990,1992). These changes can be classified as changes of atmospheric constituents, changes of surface properties, and changes of gradients of properties, which would not directly affect the energy balance, but would change the circulation.”

This statement supports the conclusions in the 2005 National Research Council Report on the need to expand climate assessments to include land use/land cover changes and regional climate change in response to regional climate forcings. The first order climate forcing of

“changes of surface properties, and changes in the gradients of properties, which would not directly affect the energy balance, but would change the circulation”

have also been discussed, repectively, in the 2005 Science article “Land use and climate change” and in the 2006 Geophysical Research Letters paper “Measurement-based estimation of the spatial gradient of aerosol radiative forcing“.

The Robock and Graf paper further state,

“It is known that about 60% of the land surfaces are changed by man; today only about 30% of the land area is wood or forest (Bernhardt and Kortuem, 1976). This implies a tremendous impact on the natural energy exhange conditions….In Europe, for example, huge areas were deforested when the Mediterranean Cultures developed. Since the soil was the completely eroded, any reforestation failed, and the Mediterranean landscape was changed permanently. This must have also had a strong influence on the regional climates.”

While the Robock and Graf studied focused on pre-industrial time, its conclusions are very much applicable to the need to include regional climate forcings of land surface processes and of aerosols, and their effect on atmospheric circulations, as major study topics in assessments such as the new IPCC Report.

The Value of Weblogs for Climate Science

Science magazine published an article on April 14, 2006 entitled “Environmental Science Adrift in the Blogosphere” (subscription required) by Alison Ashlin and Richard J. Ladle.
The Policy Forum article discussed the value of weblogs.

It specifically mentioned the Climate Science weblog in its “Supporting Online Material” as one of the “Examples of excellent, informative sites…”, along with several others including Prometheus , James’ Empty Blog, and Real Climate. There are, of course, other excellent climate science weblogs that were not recognized by Science, so ours were just examples. Nonetheless, we appreciate this recognition! The activity on our weblog has increased steadily during this period with over 138,000 hits in March.

There are several reasons for the success of science weblogs. While, not a replacement for peer-reviewed papers, the weblogs have the following attributes:

1. When peer-reviewed climate science papers are published, the major conclusions of the papers can be summarized and quickly disseminated to a wide audience. The significance of the research can be translated into a more readily understood summary.

2. If misconceptions are reported in climate science assessments and in news media reports, the weblog provides a forum to correct these misstatements.

3. The Comments component of science weblogs provides an effective medium for others to respond to the weblogs. This constructive dialog permits all of us to gain knowledge and perspective from the exchange of diverse views.

I look forward to continuing the Climate Science weblog and to the valuable exchanges of information that has been achieved. Thank you for reading the weblog, and responding when appropriate!

New CCSP Committee With the Same Conflict of Interest

A new CCSP Committee , the “Climate Extremes: Analysis of the Observed Changes and Variations and Prospects for the Future” Synthesis and Assessment Product 3.3 is being configured. This Committee suffers from the same conflict of interest that was associated with the CCSP Report “Temperature Trends in the Lower Atmosphere: Steps for Understanding and Reconciling Differences”. As written on the CCSP Web site for this new Report ,

“The lead NOAA focal point, Dr. Thomas Karl, is the Editor-in-Chief. The assistant NOAA focal point, Dr. Christopher Miller, serves as the Associate Editor. ”

The Executive Summary has

“Proposed Convening Lead Authors (CLA): Jerry Meehl, Thomas Karl”

These are well qualified scientists. However, the Editor-in-Chief again will be evaluating his own analyses and that of the organization which he leads (NCDC) . If policymakers are going to be presented with the diversity of scientific perspectives on issues, we need to move beyond inbred climate assessments.

I provided the following text in my Public Comment on the earlier CCSP Report which was ignored in the Committee Response for that Response;

“The process that produced the report was highly political, with the Editor taking the lead in suppressing my perspectives, most egregiously demonstrated by the last-minute substitution of a new Chapter 6 for the one I had carefully led preparation of and on which I was close to reaching a final consensus. Anyone interested in the production of comprehensive assessments of climate science should be troubled by the process which I document below in great detail that led to the replacement of the Chapter that I was serving as Convening Lead Author.

The inappropriate substitution of a replacement Chapter 6, for the one I had led the drafting before resigning from the Committee, enforced the narrow perspective of the Chair of the Committee. The new version replaced the version that was nearly complete and accepted by the Committee in August 2005.

This substitution represents an example of this usurpation of the responsibility granted in the original charge to the Committee and the forcing of the Editor’s perspective on this Report. The result was the elimination from the Chapter of significant scientific issues concerning temperature trends in the lower atmosphere in the version of the Report that is now under public review.

A recommendation for future Committees of this type is that,

Future assessment Committees need to appoint members with a diversity of views and who do not have a significant conflict of interest with respect to their own work. Such Committees should be chaired by individuals committed to the presentation of a diversity of perspectives and unwilling to engage in strong-arm tactics to enforce a narrow perspective. Any such committee should be charged with summarizing all relevant literature, even if inconvenient, or which presents a view not held by certain members of the Committee. Assessment Committees should not be an opportunity for members to highlight their own research and that which supports their personal scientific conclusions without properly placing into perspective the diversity found in the peer literature. When the Chair of such a committee seeks to limit the focus of an assessment Report in a specific direction, such as was the case with this Committee, the advancement of our understanding of the scientific issues involved suffers. The Editor writes in the Preface that ‘This Report promises to be of significant value to decision-makers, and to the expert scientific and stakeholder communities… Readers of this Report will find that new observations, data sets, analyses and climate model simulations enabled the Author Team to resolve many of the perplexities noted by the NRC and the IPCC in their earlier Reports.’

Stating this does not make it so. Unfortunately, the Report advocates a narrow perspective on science shared by the majority of the committee, rather than dealing comprehensively with the issues under its charge and found in the broader scientific literature. As such it does a disservice to those interested in a comprehensive review of the relevant science.”

It appears that the new CCSP Report follows on the same track.

In my March 16, 2006 Climate Science weblog, I stated,

“To remedy this very serious inbred structure of climate science assessment committees, we need for them to be properly configured. This means that scientists should not be appointed who are evaluating their own research and perspectives. They certainly should be invited to present their research and conclusions, but to have them evaluate their work and views is very inappropriate, and results in the communication of information to the policymakers which is biased.

In the November 27, 2005 issue of EOS, a news report by Sarah Zielinski Staff Writer has a quote by Antonio Busalacchi, Professor and Director of the Earth System Science Interdisciplinary Center at the University of Maryland;

â€? Busalacchi…called for the inclusion of a wider range of scientists, including international scientists, in developing these reports. In
addition, he warned that some small scientific communities had become ‘incestuous’ with report authors reviewing their own work.â€?

This description certainly applied to the CCSP Report “Temperature Trends in the Lower Atmosphere: Steps for Understanding and Reconciling Differencesâ€?, and appears that it will again be true in the new CCSP Report.

There is a Public Comment period until May 12, 2006, although from my experience with the Public Comment from the first report (see and see), the Report will not be substantively changed in response. Until the Conveners of these Climate Assessment Committees become serious in evaluating the true breadth of scientific issues associated with climate variability and change, policymakers will continue to be exposed to incomplete scientific information. With all of the controversy regarding (the inappropriate) attempts to limit the presentation of the views of Jim Hansen, it is disappointing that when others seek to present the diversity of views on climate science, their views are suppressed, as occurred with my involvement with the first CCSP Report.

One way to move forward with a balanced Committee is to include input from the American Association of State Climatologists in establishing a broader perspective on the issue of “Climate Extremes: Analysis of the Observed Changes and Variations and Prospects for the Future.” A Chair also needs to be appointed who does not have a vested interest with a particular outcome of the subject of the Report. It is very noteworthy that despite the expertise in the community of State Climatologists on the analysis of observed climate extremes, that there are none who are proposed to serve on the Committee.

The Policy Statement on “Climate Variability and Change” which the AASC has adopted clearly shows that this community has expertise that should be utilized in completing the new CCSP Report on “Climate Extremes: Analysis of the Observed Changes and Variations and Prospects for the Future”.

A Win-Win Solution to Environmental Problems

At the April 13, 2006 Session “Climate Change – What Happens in a Warmer Rockies?” at the Colorado College “State of the Rockies Conference”, there was a very informative talk by Auden Schendler, Director of Environmental Affairs at the Aspen Skiing Company. He reported on a number of technical changes that have been applied at the ski areas owned by this company to reduce the emissions of carbon dioxide. What was enlightening in his talk, however, were the benefits in all types of air quality that resulted, and that these changes saved money!

Such win-win solutions to environmental problems should be a goal of policymakers. Such a framework fits with the “vulnerability” perspective that has been advocated on the Climate Science weblog.

The newspaper High Country News in its March 6, 2006 issue had an article (subscription required) entitled “Save Our Snow” by Michelle Nijhuis. This article is headlined ” Can Aspen and other Western towns put a dent in a global problem?”, and reports on a variety of ways to reduce negative effects of environmental footprints. However, the article perpetuates the concept that the currency to use to document the negative effects is the amount of CO2 reduction. In other words, the focus should first be on greenhouse gas emission reductions with the other environmental benefits being a beneficiary of these reductions. This will be quite a challenge for Aspen, as the news report states that, with respect to the Aspen greenhouse gas inventory of emissions,

“But the inventory contained bad news, too. It showed that, despite its progressive measures, Aspen’s per-capita emissions in 2004 were almost twice the national average. The town’s commercial and private air traffic, which accounts for a whooping 41 percent of the total emissions, topped the list of contributors.”

The use of the greenhouse gas emissions is a useful “environmental currency”, however, only as long as it is provides the benefits needed to reduce the risk to critical environmental and/or social resources. It thus needs to be part of a win-win strategy in which there are a diversity of benefits. Energy efficiency and energy independence, for example, are examples in which every stakeholder benefits. Greenhouse gas emission reduction, as the “currency”, is a blunt instrument if there are more effective ways to reduce the risks to societal and environmental resources.

My recommendations are as follows:

1. The first step is to assess the societal and environmental resources that are important.

2, Then determine the threats to these vulnerabilities and what are the thresholds that once breached result in damage.

3. Create metrics to quantitatively monitor their variability and change over time, in order to assess whether thresholds are being approached. Model sensitivity studies, built around each resource, should be used to determine critical social and environmental metrics that need to be monitored. Model predictions can be included in this assessment, but only when they have shown skill in forecasting these critical social and environmental metrics.

4. In terms of policy actions, segment them into win-win options and others which involve economic cost. This information will be very useful when policy decisions need to be made.

With these recommendations, greenhouse gas emission reductions, relative to other “currencies”, can be evaluated with respect to their value to provide reductions in risk to essential social and environmental resources. In this framework, greenhouse emission reductions are only useful if they provide real benefit with respect to these resources. If a policy decision is made for other reasons, but also reduces greenhouse gas emissions, this is clearly an example of a win-win situation.

Inaccurate Climate Science Reporting

There is a news article today (April 19, 2006) by Reuters. It is entitled “Global warming hits Canada’s remotest Arctic lands”.

It provides an example of the systemic problem in many climate media reports to inaccurately report on climate science. The article includes the text,

“The eternal night which blankets the region for three months is less dark, thanks to warmer air reflecting more sunlight from the south.â€?

I have read many environmental effects begin blamed on “global warming”, but no reputable climate scientist would accept this statement as having any scientific merit. We very much need media reports that are soundly based on science; the Reuters news article clearly is not.

New Study on the Importance of Regional Climate Studies

A new paper has been published in the Proceedings of the National Academy by Christophe Barbraud and Henri Weimerskirch entitled ” Antarctic birds breed later in response to climate change”

“In the northern hemisphere, there is compelling evidence for climate-related advances of spring events, but no such long-term biological time series exist for the southern hemisphere. We have studied a unique data set of dates of first arrival and laying of first eggs over a 55-year period for the entire community of Antarctic seabirds in East Antarctica. The records over this long period show a general unexpected tendency toward later arrival and laying, an inverse trend to those observed in the northern hemisphere. Overall, species now arrive at their colonies 9.1 days later, on average, and lay eggs an average of 2.1 days later than in the early 1950s. Furthermore, these delays are linked to a decrease in sea ice extent that has occurred in eastern Antarctica, which underlies the contrasted effects of global climate change on species in Antarctica.”

This paper is a very effective example of why a focus on regional climate variability and change is needed (and why the use of global average metrics such as a global averaged surface temperature are so misleading).

The paper comments not only on bird breeding behavior, but also on recent trends in sea ice areal extent and sea ice season. They found that there has been a

“large (12-20%) reduction in sea ice extent since the 1950s..”,

but that

“…the duration of the sea ice season tended to increase by >40 days in eastern Antarctica since the late 1970s…”.

The concluded that

“Although these contrasting trends seem counterintuitive, recent research suggests that sea ice extent is connected to large-scale features of the global climate system (such as the Southern Oscillation Index or the Southern Annular Mode), whereas the length of the sea ice season is connected to more regional features such as temperature…”.

A message from this paper is that we need a regional focus on climate variabiltiy and change. The concurrent observed decrease in sea ice extent and the increase in the length of the sea ice season should also be compared with the multi-decadal global climate projections of Antarctic sea ice change to assess their skill at predicting thes trends.

New Paper on Land Use/Land Cover Change as a First-Order Regional Climate Forcing

Professor Dev Niyogi of Purdue University has alerted me to a new paper (subscription required) by B. Timbal and J. M. Arblaster in GEOPHYSICAL RESEARCH LETTERS entitled “Land cover change as an additional forcing to explain the rainfall decline in the south west of Australia” which further supports the need to include land use / land cover change in any assessment of the human forcing of the climate system (SWA is “southwest Australia”).
The abstract reads,

“A fully coupled climate model forced with natural and anthropogenic atmospheric forcings is used to investigate the rainfall decline in the south west of Australia. Results are compared between experiments with two different land covers. We found that vegetation cover affects modelled rainfall in the region and enhances the model response to anthropogenic atmospheric forcings, which were found in a previous study to explain part of the observed rainfall decline. This result is observed directly in model rainfall and using a statistical downscaling technique which relates local rainfall to mean sea level pressure and large-scale rainfall. While the rainfall response to anthropogenic forcings is driven mostly by the changes in pressure, the land cover influences directly the modelled rainfall (large-scale and total) and thus indirectly the downscaled rainfall. ”

The paper cautions that further study is needed,

“On the balance of evidence, the rainfall decline in SWA that is attributable to anthropogenic atmospheric forcing….. is likely to have been enhanced by the large-scale land clearance which occurred in SWA over the 20th century. However the magnitude of the enhancement must be treated with caution. Firstly it is a model response from a single simulation and secondly the effective land clearance in our simulation is about 4 times what was observed. Despite these legitimate uncertainties, the credibility of this result is reinforced by its consistency with a previous study (PI04). This should encourage further studies with a more realistic land clearance (magnitude and timing).”

The PI04 study is the 2004 Journal of Geophysical Research paper Pitman, A. J., G. T. Narisma, R. A. Pielke Sr., and N. J. Holbrook, Impact of land cover change on the climate of southwest Western Australia.

If this first order land use/land cover climate forcing is not included in the new IPCC assessment, it will be a serious error of omission.

Are Multi-Decadal Climate Forecasts For the Rocky Mountiains Skillful?

Yesterday, I participated in a meeting at Colorado College entitled ” 2006 State of the Rockies Report Conference“. The Report by Colorado College that was compiled for this Conference is very informative, and recommended to anyone who would like an overview of the variety of political, demographic and other changes underway in this region.

There is an important issue with the session that I was involved with, however, that is misleading in terms of how it is presented to the public and news media.

My session was entitled “Climate Change- What Happens in a Warmer Rockies?”.

A news release on the session was headlined

“Is Colorado’s Ski Industry Doomed Due To Global Warming?
Study Says Disaster Possible By 2050”

The article opened with,

“Global warming may spell disaster for much of the Rocky Mountain West’s ski industry by the year 2050, according to a climate-trends model showing dramatic snowpack loss due to climate warming. The climate model results are part of the 2006 Colorado College State of the Rockies Report Card, released this week.”

Although I am listed as a presenter at the session in the news article, the content of my talk was not reported on at all in the article. The powerpoint slides of my talk, titled ” Consequences of Climate Change and Variability in the Rocky Mountains – The Need for a Vulnerability Assessment Framework “, discuss that such forecasts have no demonstrated regional predictive skill. The news article and the specific section in the 2006 State of the Rockies Report are misleading in terms of the skill in regional multi-decadal climate projections. In the April 7 Climate Science weblog, examples of quotes by other climate scientists on the current inability to make such regional forecasts was presented.

While the study in the State of the Rockies Report is a useful “what if”, and fits into the definition of a “process” study as defined in the July 15 2005 weblog entitled “What Are Climate Models? What Do They Do?”, to communicate these model results to the public as forecasts is misleading and inappropriate.